[time-nuts] HP 5065a Rb ref update and question on time scale

Magnus Danielson magnus at rubidium.dyndns.org
Sat Oct 1 08:53:44 UTC 2011

On 30/09/11 17:46, cdelect at juno.com wrote:
> Paul,
> The time scale selection is to match the offset in each particular
> receiver section and thus put it on frequency. Once there you can use the
> chart to determine offsets from the value you use.
> The synthesizer setting by virtue of how its designed does not allow one
> digit changes! You have to use one of the settings from the chart in the
> manual to get you within the C-field range when tuning!
> Also after a synthesizer change you have to wait a long time (or remove
> and replace the red wire powering the synthesizer) for the operation
> light to reset.

I had one HP5065A with a totally non-standard setting. I put that 
setting on paper and instead chose a standard one writen down on the 
front panel. This gave me the wrong frequency, so I looked it up in the 
table of the manual and tried a few others until I settled for one 
giving me good frequency compared to by Thunderbolt locked to GPS. I the 
trimmed the C-field up for the last piece. Once I decided to got this 
route, it didn't take too much time to hit the spot. You are really lost 
without the table with it's offset ordered sets of settings.

There is a few hidden aspects to the synthesizer settings. The factor m 
and n which reshape 5 MHz to 5,312.. MHz using m/n*5 MHz is not listed. 
The n factor is n=10000-TW where as m is about 1.6 times n. The m factor 
determines the loop gain in that PLL lock. However, it is only part of 
the story, but it is interesting to note that there is a loop within a 
loop in this rubidium where as the 5,312... MHz synthesis is done using 
other methods in most other rubidiums. Dividing by 16 and mix up with 5 
is not too uncommon.


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